'''
Problem:
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 x 99.
Find the largest palindrome made from the product of two 3-digit numbers which is less than N.
'''
from __future__ import print_function

n = int(input().strip())
answer = 0
for i in range(999, 99, -1):  # 3 digit nimbers range from 999 down to 100
    for j in range(999, 99, -1):
        t = str(i * j)
        if t == t[::-1] and i * j < n:
            answer = max(answer, i * j)
print(answer)
exit(0)
